臺灣博碩士論文加值系統

本篇論闡述了在multi-carrier code division multiple access (MC-CDMA)的系
統之中，因為多重使用者接收而造成的multiple access interference (MAI)現象，可以經由選碼程序的使用來大幅降低這種干擾。在我們的系統之中，選碼程序的應用，是建構於LS(Least Square)通道估測之下。除此之外，我們的選碼方法不需要因為使用者人數的增加而重新選碼，利用了這些選碼方式，在MC-CDMA系統效能會有顯著的增加，而且複雜度不會有明顯的提升，而在後面模擬的結果可以發現這種選碼方式的優點，而且和初始值無關的特性。在本文的最後，會引入時變通道選碼的概念，為在通道隔一段時間選一次碼，經由這種概念，我們的選碼方式在時變通道也是可行的。

The paper illustrates that multiple access interference (MAI) can be reduced by re-ordering the spreading codes in multi-carrier code division multiple access (MC-CDMA) systems. An effective spreading code allocation procedure using simple least square (LS) channel estimation is presented to reduce the MAI in downlink MC-CDMA systems. Moreover, the spreading codes chosen by the method are in a consistent sequence. Using this presented code selection method, the system capacity of MC-CDMA can be effectively increased without increasing the system complexity. Simulation results show that the presented method can work well for both time-invariant and fading channels.

誌謝…………………………………………………………………………………….II
中文摘要……………………………………………………………………………….III
英文摘要……………………………………………………………………………….IV
目錄…………………………………………………………………………………….V
圖目錄………………………………………………………………………………….VII
第一章 前言………………………………………………………………………....1
第二章 CDMA多載波分碼多重存取系統介紹………………………………..….3
2-1 多重存取多工(Mulit-Access)系統的介紹…….……………………..……3
2-1-1 分頻多工(FDMA)系統的介紹…...……………………………..3
2-1-1 分時多工(TDMA)系統的介紹……………………………….….4
2-1-2 分碼多工(CDMA)系統的介紹…………………………………..6
2-2 多載波分碼多重存取系統(Multi-carrier CDMA)簡介……………………………………………………………..…..…...……….7
2-3 MC-CDMA傳送端架構(Uplink)…………………….………….………….7
2-4 MC-CDMA接收端架構(Downlink)……………….………………..……...9
2-5 無線傳輸通道模型規格和特性介紹…………………………………..……11
2-6 Walsh Hadamard碼和OVSF碼的簡介……………………………...…...19
第三章 MAI和CDMA接收檢測法………………………………..………………21
3-1 MAI(Multi-Access-Interference)介紹……………………….…………….21
3-2 EGC(Equal Gain Combining)等化法介紹……………………..............…23
3-3 MRC(Maximum Ratio Combining)等化法介紹…………….......................25
3-4 ORC(Orthogonality Restoring Combing)等化法介紹………………….…26
3-5 MMSEC(Minimum Mean Square Error Combining)等化法介紹……………………………………………………………………………... 27
第四章 選碼程序介紹…………………………………………….………………..29
4-1以選碼方式來有效降低因多重路徑所造成的MAI現象探討…………………………………………………………………….………...30
4-2 Qinghua選碼方式簡介………………………………………………...……..31
4-3最小平方法(Least Square)通道估測法之簡介………………………………34
4-4 新式選碼法介紹………………………………………………………….…..35
4-5 模擬與分析(Simulation and Analysis)………………………...….…..….…38
第五章 時變通道下的選碼程序………………………………………………...….55
5-1時變通道的衰減特性………………………………………………………...55
5-2時變通道下的選碼方法…………………………………………………..….56
5-3 選碼機制在有限位元(finite bits)的討論…………………………..……….58
第六章 結論……………………………………………………………………..…60
參考文獻……………………………………………………………………………….61

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